In IEEE 802.15.4e-2012, a wireless mesh network communication standard using Time-Slotted Channel Hopping (TSCH) Media Access Control (MAC) has been proposed. In this standard, at the time of initial connection of a node to an object network, connection authentication is performed to acquire a MAC layer cryptographic key used in the object network. For the connection authentication, a 128-bit common key unique to the object network called a “join key” is used, and only a node having the join key succeeds in the connection authentication. If a node does not have the join key to the object network, a procedure called “over-the-air (OTA) provisioning” that dynamically distributes the join key is executed on an exclusive network called a provisioning network.
The provisioning network uses the same MAC layer and physical layer as those of the object network, and is generally constructed such that wireless coverage of the provisioning network and wireless coverage of the object network to overlap with each other in order to achieve on-site join key acquisition. For connection authentication to the provisioning network, a 128-bit common key called a default join key or an open join key is used.
The value of the default join key is a fixed value opened in accordance with a standard, and the value of the open join key is a closed fixed value set in a node in advance. When a certain node succeeds in the connection authentication to the provisioning network, the join key to the object network is encrypted with a public key of this node and is distributed. This node decrypts the join key with a secret key corresponding to the public key of the node itself, thereby acquiring the join key.